Many business and science applications use computers to record data, with much of the data being stored on removable media. The removable media may take the form of a magnetic tape cartridge, an optical disk cartridge, floppy diskettes, or floptical diskettes. The advantages of storing data on removable media are numerous. These advantages include a capability of storing large amounts of data (additional cartridges can be used to store additional data), providing a vehicle for long term storage and archival, backing up data which resides on non-removable media, and allowing for easy transfer of data between computers. Often the removable media is the most economical method of retaining the stored data.
In the past, when a request for a specific removable media cartridge was made, an operator needed to retrieve the data cartridge and physically load the cartridge into the storage device. This manual mode involved a significant delay while the cartridge was being retrieved by the operator before the data on that cartridge could be processed. Additionally, the operator could easily make an error and load an incorrect cartridge.
With advancements in data storage products, the media cartridges were reduced in size and robots were designed and incorporated to automatically retrieve cartridges and load those cartridges into a storage device. The robot is housed within an automated storage library that also contained storage devices and a plurality of cartridges placed within storage cells. The robot replaced the operator and improvements were seen in access time and in reliability. However, because the robot is a complex machine requiring multiple degrees of freedom (rotation and translation about the mechanical Joints) it would require maintenance and adjustments. The robot's complexity also resulted in a significant manufacturing and maintenance costs.
The difficulties that exist with the multiple degrees of freedom within a robot have been addressed, to some degree, by using a pass-through picker. The pass-through picker is the assembly that retrieves a cartridge from a storage cell and places the cartridge into the storage device. The pass-through picker assembly is positioned within an automated storage system between the storage device and the storage cells. The storage cells are typically located parallel to and opposite the storage device. The pass-through picker retrieves a cartridge from the storage cell, passes the cartridge through its structure, and transfers the cartridge to the storage device. Although this reduces the complexity of the picker as compared to a robot, the pass-through picker limits the location of the storage cells to being opposite the storage device. As data storage products further progress, this limitation does not allow for the total number of storage cells to be maximized within the automated storage system. Additionally, there is an ever increasing need to provide still greater amounts of storage capabilities in smaller spaces. Therefore, the pass-through picker in combination with the storage device and storage cells should use space very efficiently.
What is needed is a pass-through picker having the capability to retrieve cartridges from storage cells that are located both opposite and adjacent to the storage device. This improvement would allow for the volume of the automated storage system to be populated with a maximum number of storage cells, and maintain a relatively simple mechanism as compared with a robot. Furthermore, if the pass-through picker assembly were capable of transferring a cartridge into the storage device without disturbing a cartridge that was directly opposite a load slot of the storage device, then a cartridge could be located directly opposite the storage device and the access time to load that cartridge would be minimal.